The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
With the popularization of mobile communications, mobile voice communications alone cannot meet people's requirements on information acquisition. Mobile data communication service shows its strong vitality and prosperous development prospect. One of 3rd Generation (3G) mobile communication technologies, Code Division Multiple Access 2000 1x (CDMA 2000 1x) Evolution Data Optimized (EV-DO), emerges as the times require.
The peak rate supported by the carrier frequency in each sector in 3rd Generation Partnership Project 2 (3GPP2) CDMA2000 1XEV-DO reaches 2.4 Mbps, and the peak rate of its DO revision A (DO rev A) reaches 3.1 Mbps. At present, a preliminary agreement has been made on the evolution of the air interface technology of 3GPP2 in the industry. Specifically, the evolution is divided into 2 phases: in Phase 1, multicarrier DO technology is employed, a higher peak rate is obtained by upper layer software updating, while the physical layer remains unchanged to the maximum extent, and backward compatibility may be ensured; in Phase 2, more advanced novel technology is introduced, which is a long-term evolution plan of 3GPP2.
The DO system is divided into Pilot channel, Media Access Control (MAC) channel, Control channel and Traffic channel in the forward direction. Time Division Multiplex (TDM) is employed in these channels, and fixed power transmission is adopted.
The MAC channel is further divided into Reverse Activity (RA) subchannel, Data Rate Control Lock (DRC_Lock) subchannel, Reverse Power Control (RPC) subchannel and Automatic Repeat Request (ARQ) subchannel. Code division multiplex (CDM) is employed in these subchannels. The sum of the power of the subchannels is a fixed value, which is referred to as rated power. The RA subchannel is a common channel, i.e., all the terminals share an RA channel. Other subchannels are non-common channels, and each terminal corresponds to its own channel.
For CDMA, RPC still plays an important role in the DO system. A terminal receives an RPC instruction issued by a base station and adjusts the transmit power according to the instruction, so as to guarantee the transfer quality of the reverse channel.
In addition, the base station in the DO system periodically sends a Reverse Activity Bit (RAB) indicating the busy and idle state of the system according to the current load. The terminal determines the reverse transmit speed by itself via an algorithm according to the received RAB.
In a DO rev A system, there is a Hybrid Automatic Retransmission Request (HARQ) mechanism in the reverse direction. When data is retransmitted, the data packet transmitted in the reverse direction may be divided into several subframes. After each subframe is transmitted, the terminal checks the forward ARQ subchannel. If the ARQ indicates that the base station has received the subframe successfully, the terminal terminates the transmission of the packet in advance, and the remaining subframes are not transmitted.
Thus, it can be seen that the transfer quality of the RPC/RAB/ARQ in the forward direction has an important effect on the reverse channel. If the RPC is received incorrectly, interference may be caused due to too strong power and the reverse capability may be lowered, or the reverse quality may be affected due to insufficient power. If the RAB is received incorrectly, the reverse speed of the terminal may be too high, the transfer quality may be lowered and overload may be caused, or the reverse speed of the terminal may be too low, the transfer time delay may be increased and the system capability may be wasted. Moreover, once an error occurs on the ARQ subchannel, a successfully received subframe may be transmitted repeatedly and the system capability may be wasted, or a subframe that has not been transmitted successfully may be terminated incorrectly and an error may occur.
The CDMA technology is still employed in reverse link of the DO system. The reverse channels are divided into reverse access channel and reverse transfer channel. The reverse transfer channel further includes pilot channel, Reverse Rate Indication (RRI) channel, Data Source Control (DSC) channel, Data Rate Control (DRC) channel, Acknowledge (ACK) channel and Data channel, etc.
In the multicarrier communication system, there exists a problem of forward and reverse carrier channel configuration, including how to configure the channel and subchannel on each forward carrier as well as the reverse carrier channel corresponding to each subchannel on each forward carrier, etc. For example, to support a reverse carrier in which DRC is transmitted, the RPC subchannel, ARQ subchannel and DRC_Lock subchannel should exist in the forward MAC channel. The RPC subchannel controls the power of the reverse channel, the ARQ subchannel acknowledge the reverse channel, and the DRC_Lock subchannel indicates the reception quality of the reverse DRC. However, to support a reverse carrier in which no DRC is transmitted, only the RPC subchannel and the ARQ subchannel need to exist in the forward MAC channel, where the RPC subchannel controls the power of the reverse channel and the ARQ subchannel confirms the reverse channel, while the DRC_Lock subchannel is not needed any more. The problem of carrier channel configuration is especially apparent when the forward and the reverse channels are not symmetrical.
During the process in which a new reverse carrier is added, when the demand of reverse traffic exceeds that of forward traffic, i.e., when the number of the reverse carriers needed exceeds the number of the forward carriers needed, some redundant forward carriers may appear in the method that follows the monocarrier DO system in the prior art, in which the number of the forward carriers and the reverse carriers is kept consistent. These redundant forward carriers only send the MAC channels of the corresponding reverse carriers, including the RPC subchannel, the ARQ subchannel and the DRC_Lock subchannel, while no forward data is carried. Although the corresponding reverse carriers do not need to receive the forward channel data, the DRC still needs to be transmitted, so that the network may control the power of the forward MAC channel and perform other corresponding operations. Thus, although the terminal does not receive any data on the redundant forward carrier, the terminal still needs to transmit the DRC.
Apparently, in this processing method, the number of the forward carriers is not less than the number of the reverse carriers, and all the reverse carriers transmit the DRC. Therefore, the flexibility of the system is lowered, the load of the terminal is increased, and the battery life of the terminal is shortened. Specifically, because the number of the forward carriers cannot be less than the number of the reverse carriers, the allocation efficiency and flexibility of the system are lowered. Although the terminal does not receive any data on the redundant forward carrier, the terminal still needs to transmit the DRC; in other words, all the reverse carriers need to transmit the DRC, so that the load of the terminal is increased, and the battery life of the terminal is reduced.
When the number of the reverse carriers needed exceeds the number of the forward carriers needed, in another prior art, it is allowed that the number of the forward carriers may be less than the number of the reverse carriers. Thus, some reverse carriers have no corresponding DRC to report, and because the reverse carrier is allowed not to transmit DRC channel, the transmit power may be saved on the terminal. At this point, the forward DRC_Lock subchannel is not needed either.
In still another prior art, in addition to the forward MAC channel (including RPC, ARQ and DRC_Lock subchannels) corresponding to a reverse carrier in which DRC is transmitted, the forward carrier may further carry forward MAC channels (including RPC and ARQ subchannels) corresponding to other reverse carriers in which no DRC is transmitted. The system may allocate a plurality of MAC channel indexes to a forward carrier via a Traffic Channel Assignment (TCA) message, wherein a MAC channel index is allocated to the forward MAC channel (including RPC, ARQ and DRC_Lock subchannels) corresponding to the reverse carrier in which DRC is transmitted; and other MAC channel indexes are allocated to the forward MAC channel (including RPC and ARQ subchannels) corresponding to the reverse carrier in which no DRC is transmitted.
In the prior art, a plurality of forward MAC channels (one MAC channel includes an RPC subchannel, an ARQ subchannel and a DRC_Lock subchannel, and other MAC channels include an RPC subchannel and an ARQ subchannel) may be carried on a forward carrier, and a plurality of reverse carriers may be supported. Therefore, the number of the forward carriers allocated by the system may be less than that of the reverse carriers, so that flexibility may be improved. Meanwhile, some reverse carriers do not need to transmit DRC channel, so that power may be saved.
However, in practical applications, following problems exist in the prior art. Specifically, each forward carrier can support only one MAC channel corresponding to the reverse carrier that transmits the DRC and a plurality of MAC channels corresponding to the reverse carriers that do not transmit DRC. Therefore, this prior art is only suitable for the case in which the number of the forward carriers is less than that of the reverse carriers, but does not support the flexible allocation of the reverse carriers and the forward carriers that carry the corresponding forward MAC channels (including RPC, ARQ and DRC_Lock subchannels), so its application scenarios are limited, and the flexibility of the system is not as high as required. Especially in some special applications, for example, for the services where the difference between the reverse transmission quantity and forward transmission quantity is great and the services that change rapidly, the requirements of the services cannot be well met, and the terminal transmit power and other resources cannot be saved to the maximum extent.